Coordination Chemistry of Potentially S,N,N py -Tridentate Thiosemicarbazones with the {Re(CO) 3 } + Fragment and Formation of Hemiaminal Derivatives.

Nine potentially S,N,N py -tridentate thiosemicarbazones (HL) derived from pyridine-2-carbaldehyde or 1-(2-pyridyl)ethanone have been prepared and fully characterized. The X-ray crystal structures of six of them and two hydrochlorides were determined and analyzed. The reaction of the [ReX(CH 3 CN) 2 (CO) 3 ]/[ReX(CO) 5 ] (X = Cl and Br) precursors with these ligands yielded different kinds of compounds: the adducts [ReX(HL)(CO) 3 ], in which the ligands were S,N-bidentate; the trinuclear species [Re 3 Cl 2 (L 23 )(HL 23 )(CO) 9 ]; and the thiosemicarbazonate compounds [Re(L)(CO) 3 ], where the ligand is S,N,N py -tridentate. Besides, the reaction in methanol or ethanol of the thiosemicarbazones derived from aldehydes yielded S,N,N py -tridentate hemiaminal cationic [Re(HL OR )(CO) 3 ]X and neutral [Re(L OMe )(CO) 3 ] complexes after the coordinated ligand underwent addition of the alcohol group to the imine bond. The reactivity of the complex [ReX(HL)(CO) 3 ] in MeOH and NEt 3 led to the formation of dinuclear [Re 2 (L) 2 (CO) 6 ], where the thiosemicarbazonate is again S,N-bidentate. The influence that the substituents on the thiosemicarbazone ligands have on the stability of the complexes and the effect of the reaction medium on the resulting compounds have been analyzed.